Metal forming by explosive force through a solid gel



July 24, 1962 F. T. CALLAHAN METAL FORMING BY EXPLOSIVE FORCE THROUGH A SOLID GEL Filed June 2, 1958 4 Sheets-Sheet 1 Flag.

7 ATTORNEYS July 24, 1962 F. T. CALLAHAN METAL FORMING BY EXPLOSIVE FORCE THROUGH A SOLID GEL Filed June 2, 1958 INVENTOR.

FRED T. CALLAHAN A TTORNE VS 5 y 1962 F. T. CALLAHAN 3,045,339

METAL FORMING BY EXPLOSIVE FORCE THROUGH A SOLID GEL Filed June 2, 1958 4 Sheets-Sheet 5 IINVENTOR. ERED T. CALLAHAN A TTOR July 24, 1962 F. T. CALLAHAN 3,045,339

METAL FORMING BY EXPLOSIVE FORCE THROUGH A SOLID GEL Filed June 2, 1958 4 sheets-Shea 4 F19. IF

INVENTOR. FRED T. CALLAHAN BY M2.

A TTORNE Y5 United States Patent 3,045,339 METAL FORMING BY EXPLOSIVE- FORCE THROUGH A SOLID GEL Fred T. Callahan, Jennings, Mo., assignor to Olin Mathieson Chemical Corporation, East Alton, 11]., a corporation of Virginia Filed June 2, 1958, Ser. No. 739,195 16 Claims. (Cl. 29-421) This invention relates to the deformation of metal, and more particularly to the deformation of metal by the high pressures produced by the initiation of explosives. More specifically, this invention is directed to a process for subjecting metal, such as metal tubes, sheet metal and the like, to the expansive force of explosives while confined in a die, in order that the metal may be deformed against the die Wall.

Heretofore the working of metal has been accomplished by the familiar cupping, drawing, extruding, dimpling or swaging operations conventionally in current use. However, these operations have been found to be inadequate for working of metals demanded in highly advanced technological fields. For axample, the aircraft industry has made'tremendous strides in recent years relative to service ceilings and speed of aircraft. These advances plus future anticipated advances require, for continued improving performances, lighter, stronger and tougher materials with decreased dimensional tolerance of component parts. Many of these parts cannot be manufactured to specifications employing present conventional methods. As disclosed on pages 112 to 115 in the January 14, 1957, issue of the American Machinist, the metals presently demanded for the aircraft industry necessitate not only the working of tough metal such as titanium alloys, but also the forming of the metal into complex shapes and curvatures, which render the conventional hydro-press, drop-hammer, and other conventional methods impractical. A particular disadvantage in working of certain metals is the prohibitive amount of spring back experienced on pressure release of conventional equipment. In addition, the use of conventional methods in forming operations often require the useof secondary finishing operations. Also, metals such as various titanium alloy-s, Monel metal and various stainless steels cannot be adequately worked by the conventional methods enumerated above without elaborate and expensive auxiliary equipment and processes.

In as much as more drastic advances are contemplated in various technological fields in addition to aircraft, as for example missiles and rockets, working the metals to the contours and curvatures required can be satisfied only by more drastic methods of working, as for example the utilization of explosive charges.

Heretofore the working of metal by the force of explosive charges comprised the placing of the metal to be worked against the surfaces of a die having the configuration desired to be imparted to the metal, and subjecting the metal to the direct force of anexplosive charge. An illustration of the application of this priciple to the working of a tube is disclosed in U.S. Patent No. 2,214,226."

However, the above described method of working metal with explosive charges has inherent disadvantages when 1 used with certain explosive charges, such as black powder and mercury fulminate, in that they produce corrosive combustion products which attack the surface of the metal. In addition, problems are experienced when pressurizing large volumes, as for example in a 6% inch diameter by 28 inch long stainless steel tube. To solve these problems greater quantities of explosives have been attempted to be utilized with corresponding difficulties in complete ignition of the charge together with the obvious 3,045,339 Patented July 24, 1962 disadvantage of added quantity requirements of the charge and corresponding hazards.

An alternative solution =to'the above was the process disclosed in Swedish Patent No. 105,422 and No. 115,846 wherein the force. of the explosive charge was transmitted to the metal to be worked through a liquid hydraulic medium. Various other liquids such as oil and the like have also been attempted. However, the use of liquids presented has, as'is obvious, the inherent disadvantages of requiring elaborate sealing means against leakage, particularly for example in the fabrication of complex parts, not only for the part to be formed but also in the die means employed. These disadvantages and others in herent in the use of liquids prevented their acceptance in industry and necessitated the investigation of other transmitting mediums.

Other mediums investigated for transmitting the full effect force of an explosive were rubber materials presently in use in conventional metal forming, tars, putty, soft clays, muds and low melting materials such as wax, aluminum, lead and woods-metal. Various inherent disadvantages of these materials, such as damping of the explosive force, inflammability, and/or absorption of the explosive force, to cause plastic flow of the medium, have prevented, as with liquids, their acceptance in industry.

It has been discovered that a gelatinous colloidal solution in its solid phase, a gel, either organic or inorganic,

- and either a hydro-or an alco-gel transmits the full effect of force of an explosive to the metal to be worked without the disadvantage of the prior art. In addition the use of a gel provides anadvantage of a solid in handling.

Accordingly, it is the object of this invention to provide a novel process eliminating the disadvantages of prior art.

Another object of this invention is to reduce the complexity of presently used forming techniques.

A further object of this invention is to provide a noval process which eliminates the need for secondary finishing operations.

A still further object of this invention is to provide a process utilizing a novel transmitting medium for the force of explosive charges in metal forming operations.

A still further object of this invention is to provide a process employing a noval force transmitting medium which has the advantages of both a solid and a liquid.

Other objects and advantages become apparent from the following description and-drawings in which:

FIGURE 1 is a cross-sectional view of an application of the invention illustrating the bulging of a metal tube;

FIGURE 2 is a cross sectional view of another application of the invention utilized in bulging a metal tube;

FIGURES 3, 4 and 5 are cross-sectional views of the steps employed in practicing an application of the inven tion;

FIGURES 6 and 7 are cross-sectional views illustrating an alternative process of practicing another application of this invention;

FIGURE 8 is an isometric cross-sectional view of a seal employed in FIGURES 6 and 7;

FIGURES 9 and 10 are cross-sectional views of still another application of the invention;

FIGURES 11, 12 and 13 are cross-sectional views illustrating the application of the invention to the formation of complex shapes and curvatures;

FIGURES 14 and 16 are cross-sectional views illustrating an application of the invention in the forming of closed-end vessels; and

FIGURES 15 and 17 illustrate the articles obtained in the embodiments of FIGURES l4 and 16, respectively. Generally speaking, the objects of this invention are accomplished bypreparing a gelatinous colloidal solution,

pouring the solution adjacent the surface of the metal to be formed and permitting the solution to gel into a solid phase. This assembly, of metal and gel, can be conveniently handled for transporting it and placing in a die without the necessity of requiring seals, against leakage, as in the case of liquids. Upon placement of the metal and gel into a suitable die, the gel is subjected to the force of an explosive charge whereupon it transmits the full effect of the force to the metal to be worked whereby it is possible to obtain all of the advantages of forming metal with explosive charges.

FIGURES l and 2 illustrate an application of the invention of the bulging of a metal tube. More specifically, with reference to FIGURE 1 the metal tube 27 is filled with a gelatinous solution and permitted to stand until its phase changes to a gel 5. Any gelatinous solution capable of forming a gel, reversible or irreversible, is operative in the process irrespective of source whether animal protein or vegetable. The sole requirement is that it form a solid phase which permits the handling of the gel without danger of leakage such as from liquids. An example of the gelatinous solution illustrating the above, is a 20% solution of 100 Bloom technical grade gelatin derived from animal protein based on a weight to volume formulation that is, 20 grams of gelatin per 100 milliliters of Water. Exceptional results were obtained with this specific gelatin through a 5 to 35% range.

Tube 27 with gel 5 can be manipulated without danger of the gel flowing or leaking out of the tube. As noted above, the use of a gel as a transmitting medium for the force of an explosive charge provides a specific advantage over use of liquids, such as water, oil and the like, in that no sealing means are necessary to maintain the gel within the tube. After gelling, tube 27 is placed Within a split female die 11.

Die 11 consists of two identical portions having their interior portions machined to provide cavities 12 and 17, defining the bulges desired to be formed in the tube, and bores 28, 29 and 30 of a diameter conforming to the dimension desired in the unbulged portion of the tube. Upon assembly of the die portions containing tube 27, the assembly is placed within a die holder 13 also consisting of two identical portions.

Die holder 13 contains an interior chamber 26 adapted to receive die 11, and a bore 21, provided in the left end of the holder, which communicates with chamber 26. Although not essential, the ends of the holder are adapted to provide, upon assembly, circular openings 14 and '18 for convenience in reaching circular inserts 16 and 19, as to bleeding means for pressures developed within the assembly. These inserts are mounted Within peripheral grooves 15 and 20 provided in die holder 13.

Bore 21 is filled with an explosive charge 22 in which is embedded a detonator 23 having leads 25 extending through a small sealed opening 24 in one of the inserts 19. Although a detonator has been shown, the explosive may be of any composition in which self-detonating means is self-contained. In addition, various types of explosives may be used in practicing the invention, for example, the charge may be either a low velocity propellant or a high velocity explosive. The selection of the explosive is governed by the ballistic requirements needed for the working of the metal, and/or the shape into which it is to be formed. Although the correlation of explosive charge to metal forms no part of this invention, it is pointed out that a proper selection of the explosive will provide a controlled rate of forming, wherein the metal can be moved during condition of plastic flow which will not only prevent the accumulation of stresses which result in fractures but in which the metal is also work hardened. The selection of charges will also depend upon their burning speed, impetus, progressivity and pressure-peak to time relationship. By proper selection of explosives it was possible to form one inch tubes of, either type 310 or K 304, stainless steels wherein an elongation of 50% was obtained. In other tests of the similar tube, there was no measurable spring-back in the metal when the explosive selected gave the pressure at or in excess of 15,000 pounds per square inch.

Die holder 13, with the above described assembly, is placed within any convenient clamping means capable of exerting sufficient force, F, to hold the assembly against separation on the initiation of the explosive force. The clamping means may be by a series of nuts and bolts disposed about the perimeter of the die holder, or the assembly may be placed within any convenient hydraulic press. The pressure exerted by the clamping means also maintains the die holder 13 and insert 16 in sealing relationship to contain the combustion products of the explosive charge within the assembly.

With die holder 13 within the clamping means, the explosive is initiated by making an appropriate electric contact across leads 25 whereupon the charge 22 is exploded. The force of the exploded charge is transmitted through gel 5 to the walls of the tube forcing the tube against the configuration of die 11. The tube in this manner has imparted to it two bulges conforming to the cavities 12 and 17 of the die. In practice the pressure generated by the explosive, in the die assembly, was gradually released by slowly relieving the force of the clamping action maintained on the holder. However, if desired, an appropriate bleeding means may be provided in either the die holder 13, or in one or both of the inserts 16, to relieve the contained pressure within the assembly. Also, an appropriate sealing arrangement may be provided between die 11 and ends of tube 27 to prevent the gel from being forced into the die by the explosive force. If a reversible gel is used the heat developed upon initiation of the explosive charge will convert some or all the gel into its liquid phase. Therefore, to prevent the entry, or leakage, of any of the gelatinous solution between the walls of the female die and the tube, any convenient sealing means may be employed between the walls of the die and the ends of tube 27. However, a novel and preferred form of a sealing means having increased elfectiveness with increased pressures will be described hereinafter.

It was found that a secondary and definite advantage resulted in the use of a reversible gel as a force transmitting medium, in that the gel may be recovered and reused over and over until it decomposes or until bacterial action occurs, which in practice was found to impart to gelatin an intolerable obnoxious odor. In the use of gelatin derived from animal protein the gelatin was reused 10 to 15 times before it was discarded.

FIGURES 3, 4 and 5 disclose the preparation of a tube containing a gel for use in FIGURE 2. An explosive 2 is suspended by means of lead wires 3 within a tube 1. The tube is placed on any convenient flat surface 31, preferably a resilient surface to provide a liquid seal at the bottom of the tube, and the tube is filled with a gelatinous solution 4. Upon converting the gelatinous solution 4 into a gel 5, the tube is placed in a split female die 6 which has a cavity 10, machined to the ultimate dimension of the bulge desired to be imparted to tube 1, and bores 32 conforming to the ultimate dimension of the unbulged portion of tube 1.

Die 6 is provided with peripheral grooves 8, in which are mounted steel end inserts, or plugs, 9. For convenience, circular openings 7, in the assembled die, are provided for access to inserts 9. A small opening 33 is provided in one of the inserts 9 for leads 3, which is sealed after threading through of the leads. The die assembly is then placed within any convenient clamping means, and a suitable electric circuit is made across leads 3 to initiate the explosion of charge 2. The force resulting from the explosion of charge 2 is transmitted through the gel medium 5 to the walls of tube 1 to force the tube against the configuration of the die. The resultant tube has a bulge conforming to cavity 10 of die 6.

As noted above, appropriate sealing means may be employed between die 6 and tube 1 to prevent any converted liquid or liquid phase'of gel 5 to be forced between die 6 and tube 1. Also, although charge 2 may be embedded or spaced in any portion of gel 5 within tube 6, it has been found that optimum results occur when the charge is positioned opposite or centralized between the area to be worked. Thus, in FIGURE 2, charge 2 is centrally placed between that portion of cavity 10 which will impart to the tube its largest outside diameter. Accordingly, if a dual bulge'is to be imparted to the tube as in FIGURE 1, two charges may be employed,

. which are positioned at the cavities of the die, which cavities would correspond to elements 12 and 17 in FIG- URE 1. Alternatively, for a dual bulged tube a single charge may be placed or positioned within the tube at a point intermediate the bulges.

In the preferred application of the invention, as noted above, some obturating sealing means are employed in the ends of the tube to be formed. Although various sealing means may be employed, novel and preferred means employed in FIGURES 6 and 7 involve the placing of a resilient cup-shaped obturating seal 34 in the bottom of tube 1, wherein the flanges are inwardly disposed within the tube. An explosive charge 2 is suspended by means of lead wires 36 within the tube. Lead wires 36 are separated so that upon insertion of a second seal 35, identical to seal 34, the lead wires leave the tube between seal and the inner walls' of tube 1. After the charge has been suspended in the tube, the tube 1 is filled with a gelatinous colloidal solution 37. After filling of the tube with the solution, end seal 35 is inserted, in inwardly disposed relationship, in the open end of the tube. Since seal 35 is resilient, any excess solution within the tube will be forced out between the walls of the tube and the flange of the seal.

After assembly of the tube, the gelatinous solution is converted into a gel 38, and the tube is then placed within the die of FIGURE 2. FIGURE 8 illustrates an isometric cross-sectional view of seal 34 employed in FIG- URES 6 and 7, which illustrate a seal constructed of any resilient sealing material formed into a base39 and an annular axial flange 40. In the use of this novel seal 34 the force transmitted in gel 38 forces flange 40 outwardly against the inner walls of tube 1. The pressure at which flange 40 contacts to the wall of tube 1 will be in proportion to the amount of force, of the explosive, exerted within the tube 1. Accordingly, the effectiveness of seal- .ing will increase with increasing pressures.

Since, as noted above, in the use of a reversible gel, the heat generated in the explosion of charge 2 will convert some of the gel into a liquid phase, the specific seal 34 described above insures to maintain both, the liquid and solid phases of gel 38 within tube 1 to prevent the gel from being forced between the outside wall of the tube and the face of thedie. In addition, the maintenance of the gel within the tube, by the seals, provides for the complete recovery of the gel for reuse, without losses of the 'gel as would occur in the absence of the seal.

FIGURE 9 illustrates an application of the invention to the forming of a simple dish shaped sheet metal structure. A split female die holder 41 containing a chamber 42 is provided with peripheral grooves 43 in which are mounted steel insert seals, or plugs, 44. A bore 45 in the other end communicates with chamber 42 and is provided at its extreme end with a peripheral groove 46. Bore 45 and groove 46 are adapted to receive a breech mechanism 47 which in turn is adapted to receive a cartridge 48 and a suitable means, not shown, for pouring in of a fluid. Y

. A die 49 containing a dish shaped cavity is mounted within chamber 42 on insert 44. Die holder 41 is then turned on end and a sheet of metal 51 is placed on die 49 over cavity 5%). As described above, appropriate sealing means may be employed between the perimeter of the metal 51 and the walls of chamber 42. In the upright position a gelatinous solution is poured within chamber 42, and the solution converted into a gel 52. Alternatively, the gel may be pre-fonned to conformance of the shape of chamber 42, in which form it may be inserted into the chamber of the die-holder. In its pre-form shape the gel may be handled as a solid, while possessing, after insertion, the characteristics of a fluid in transmitting the force of an explosive charge.

Upon initiation of cartridge 48, the force of the explosive contained within the cartridge is transmitted to the gel which in turn transmits the foce to the metal 51 to force the metal 51 against the die to impart to it the configuration of the die. In this manner various cup-shaped metal parts may be formed, as also various corrugated metal diaphragms for control apparatus.

FIGURE 10 illustrates the working of the sheet of metal 51 of FIGURE 9 wherein the explosive charge 53 is suspended within chamber 54 of die 55 during filling of the chamber with a gelatinous solution which is converted into a gel 52. Also, as above in FIGURE 9, the charge may be embedded in the gel during pre-forming. The lead wires 56 are threaded through a small hole 57 in one of the steel inserts 58 which hole may then be sealed. The die holders 41 of FIGURE 9 and die holders 55 of FIGURE 10 are placed within any convenient clamping means which exert a force, F, to hold the die against separation under the force of the explosion within.

FIGURE 11 illustrates an example of the complex curvatures possible with the invention. A split female die 66 containing a serpentine configuration 69 and cavities 61 has mounted within it a serpentine tube 62 containing a gel 63. An appropriate breech mechanism 64 is mounted within the die and adapted to contain a car tridge 65 which, upon initiation, exerts an explosive force on gel 63. The two. halves of the die are assembled and placed between any convenient clamping means to prevent separation of the die under the force of explosion.

In this application the resultant tube may contain a plurality of bulges along its serpentine path.

FIGURE 12 illustrates an application of the invention in which the tube 67 may be formed against a man drel 68. A die holder assembly such as employed in FIGURE 10 has mounted on it a mandrel 68 extending from a base 69 mounted in chamber 54 against insert 58. A steel tube 70 is slidably mounted on mandrel 68 against base 69 and the free end capped by a cap 71 which is detachably fixed to metal 68 by any convenient means such as by means of a screw arrangement. The ends of steel tube 67 may be sealed against base 69 and cap 71 by any conventional means available. The specific mandrel illustrated in this application has a screwthreaded configuration. The die holder 55 is stood up on end and a charge 53 suspended within chamber 54 prior to the filling of the chamber with a gelatinous solutaining complex configuration other than that of FIG- URE 12. The steps involved in the process of this application are identical to that of FIGURE 12. However, the mandrel in this application is formed of a material having a lower melting point than that of the tube but capable of withstanding deformation under the explosive charge. The material, for example, may be woods-metal of any composition. When steel tubes are worked, as

in this application, the mandrel may also be composed of aluminum. After working of the metal, the mandrel 74 together with cap 76 and base 75 may be removed from the die with tube 73, and the mandrel melted from within the tube.

FIGURES 14 and 16 represent the application of the invention to the working of closed-end vessels in the formation of a doorknob 77 of FIGURE and a tumbler 78 of FIGURE 17, respectively. A tubular article 79 is placed within a die of the type disclosed in FIGURE 2. As described in the applications in FIGURE 2, a tubular article 79 has suspended within it a charge 80 prior to filling with a gelatinous solution which is converted into a gel 81. The die cavity 83 is shaped to the configuration of the doorknob desired. The initiation of the explosion forms the tubular article 79 against the sides of cavity 83 to form the doorknob 77 of FIGURE 15.

In the application of FIGURE 16 a tubular article 79 similarly contains an explosive charge 80 suspended in a gel 81 but, however, differs from the previous embodiment in that the open end of the tube contains a resilient obturating sealing member 82, and wherein the cavity 84- of the die is machined into a frusto-conical configuration. On initiation of charge 80, the force of the explosive is transmitted through gel 81 to the walls of the tube '79, to force the walls of the tube against the die to form the tumbler-shaped article 78 of FIGURE 17. It is to be noted in the above applications, that the charge may be embedded within the gelatin with lead wires extending out of the die, and positioned in the gel anywhere relative to the area of the metal to be worked, or the charge may be, preferably as noted above, positioned opposite the area of the metal to be worked to obtain the optimum effect of the shock wave of the explosive. As also exemplified in the application above, the charge may be positioned adjacent the mass of the transmitting medium. Also as noted above, the force transmitting medium of this invention is any gelatinous solution which is converted into a gel, which gel provides the advantages of both a liquid and a solid medium. In the liquid phase the medium fiows into any complex form against the sides of the metal to be formed such as illustrated in FIGURE 11. Upon gelling into a solid phase the liquid may be safely and readily transported without any danger of the medium flowing or spilling out.

In addition, as will be noted in the following example, the addition of various additives, such as anti-foaming compounds, stabilizers, anti-bacterial agents and the like, which do not prevent the gelling of the solution may be included in the gel, since they only enhance the stability and working of the force transmitting medium. As brought out above, a gelatinous solution forming a reversible gel may be recovered after each working, and reused on regelling in additional workings.

With reference to a specific example, a tube, of a 3 /2- inch diameter by inch length, of 0.025 inch gage 321 stainless steel of the following composition, carbon 0.80 maximum, chrominum-17.00 to 19.00, nickel-8.00 to 11.00 and other elementsTi.5XC minimum, was prepared in accordance with FIGURES 6 and 7 and formed in the die illustrated in FIGURE 2.

In the above tube, a resilient obturating cup illustrated in FIGURE 8 was inserted in the end of the tube, whereupon the tube was uprighted on its closed end. An explosive was suspended within the tube with the lead wires separated and bent over the top of the tube.

The specific explosive employed in the example was 350 grains of WC-440H powder prepared by impregnating, 80% by weight, nitrocellulose with, 20% by weight, nitroglycerin. The charge was placed within a conventional plastic container, and a detonator with suitable lengths of lead wires fitted within the cap closing the container.

Forty gallons of a gelatinous solution were prepared by mixing 20% by weight of gelatin, derived from animal protein and having a Bloom strength of in water with agitation. After suitable agitation a colloidal solution was obtained to which 15.2 grams of sodium benzoate and an anti-foaming agent were added. The solution was then poured within 1 inch of the tube in which the charge is suspended. It is pointed out that in the example, the charge, as in FIGURE 2 was positioned so that it would be between the circumference of the largest diameter of the bulge desired to be" imparted to the tube. After filling of the tube with the gelatinous solution, a second resilient obturating seal, of FIGURE 8, was inserted in the open end of the tube, and the lead wires were externally threaded between flange of the seal and the wall of the tube. This assembly was then permitted to cool until the solution was converted into a gel.

The tube assembly was then inserted in the die cavity illustrated in FIGURE 2. The lead wires were threaded through a small hole 7 in one of the inserts 9 which was then mounted in groove 8. The die assembly was then placed in a ton hydraulic press which was adjusted to slowly build up a pressure of 100 tons, F, on the die to prevent its separation under the force of the explosive charge. To insure against any possible malformation of the tube walls due to air being trapped between the tube and the die walls, the die was connected to a vacuum pump which pulled at least 25 inches, mercury, of vacuum in the die. The lead wires were then connected to a remotely positioned detonating apparatus from which point the electric circuit was applied across the lead wires to initiate the explosion of the charge.

As noted above, to relieve the pressure contained within the die as a result of the explosion, a suitable bleeding mechanism may be utilized in the die. However, in the instant example, the pressure was relieved by a slow and gradual opening of the press with a corresponding decrease of the force F holding the dies against separation. After equalization of the pressure within the die, the die was opened and the tube removed. The gel was then dumped into any convenient reservoir for reuse in later operations. Any gelatinous scale or gel remaining within the tube was washed away by rinsing with hot water. Upon inspection of the tube, the bulge imparted to the tube was found to conform to the cavity of the die with no measurable spring back, and with 25 to 30 percent elongation.

Although the invention has been described with reference to specific embodiments, materials and details, various modifications and changes will be apparent to one skilled in the art. The invention, therefore, is not to be limited by such embodiments, materials and details except as set forth in the appended claims.

What is claimed is:

1. In the process of working metal vessels with explosives, the improvement comprising the steps of positioning an explosive charge within a vessel, and transmitting the force of said explosive charge to said vessel through an intervening gel, said gel being at least initially solid during transmission and sealed in said vessel by a resilient cup-shaped obturator, and said gel having said explosive charge embedded therein.

2. The process of claim 1 wherein said gel is reversible.

3. The method of working metal comprising, suspending an explosive charge in a metal tube in substantially spaced relationship therefrom, filling substantially all of the space between said charge and said tube with a gelatinous colloidal solution, converting said solution to a substantially solid gel, placing said tube, gel and explosive in an enclosing die having a configuration adjacent the side thereof desired to be imparted to said tube, and igniting said explosive whereby said gel is expanded so that the tube is caused to expand against said die.

4. The method of claim 3 wherein said gel is reversible, thereby adapting the gel after expansion of the tube a to be removed by the further step of pouring preparatory loidal solution, converting said solution to a solid gel,

sealing each of the open ends of said tube with a resilient cup-shaped obturator the side wall of which is inwardly disposed in said sealed tube, placing said tube, solid gel and explosive in an enclosing die having a configuration adjacent the side of said tube desired to be imparted to said tube, and initiating said explosive whereby said gel is expanded sufficiently so that said tube is caused to expand against said die.

8. The method of claim 7 wherein said gel is reversible.

9. The method of claim 7 wherein said explosive is suspended in said tube with said explosive extending axially in centered relationship with said tube to, extend axially in centered relationship to a position adjacent the area of the tube to be Worked.

10. The method of claim 9 wherein said tube has one closed end.

11. The method of bulging the walls of a sheet metal vessel comprising suspending an explosive charge in said vessel in substantially axially disposed relationship, filling substantially all of the intervening space between said charge and said vessel with a gelatinous colloidal solution, converting said solution to a solid gel, placing said vessel, solid gel and explosive in an enclosing die having a configuration adjacent the side thereof desired to be imparted to said vessel, and initiating said explosive charge whereby said gel is expanded sufiiciently until said vessel is caused to expand against said die.

12. The method of claim 11 wherein said explosive is suspended in said vessel at a position adjacent the area of the tube to be worked.

13. The method of working a metal vessel comprising suspending an explosive charge in said vessel, filling at least part of the remaining space between said charge and said vessel with a gelatinous colloidal solution, converting said solution to a solid gel, sealing the open end of the said vessel with a resilient cup-shaped obturator with its sidewall inwardly disposed in said vessel, placing said vessel, gel and explosive charge in an enclosing die having a configuration desired to be imparted to said vessel, and initiating said explosive charge whereby said gel is expanded sufficiently within said vessel so that the vessel is caused to expand against said die.

14. The method of deforming metal comprising placing one side of said metal adjacent a die having the configuration desired to be imparted to said'metal with said die being provided With a chamber enclosing said metal and said configuration of said die, placing in said chamber a solid mass of gel adjacent the other side of said metal, and subjecting said gel to a force of an explosive charge whereby said force is transmitted to said metal to deform it against the configuration of said die.

15. The method of claim 14 wherein said explosive charge is embedded in a preformed body of said gel.

16. The method of claim 14 wherein said gel is reversible.

References Cited in the file of this patent UNITED STATES PATENTS Sweden Feb. 19,

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,045,339 July 24, 1962 Fred T. Callahan It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as V corrected below Column 9, line 25, strike out "to extend"; line 26, for "axially in centered relationship to" read at Signed and sealed this 27th day of November 1962.

(SEAL) Attest:

X mm m ttesting Officer Commissioner of Patents 

1. IN THE PROCESS OF WORKING METAL VESSELS WITH EXPLOSIVES, THE IMPROVEMENT COMPRISING THE STEPS OF POSITIONING AN EXPLOSIVE CHARGE WITHIN A VESSEL, AND TRANSMITTING THE FORCE OF SAID EXPLOSIVE CHARGE TO SAID VESSEL THROUGH AN INTERVENING GEL, SAID GEL BEING AT LEAST INITIALLY SOLID DURING TRANSMISSION AND SEALED IN SAID VESSEL BY A RESILIENT CUP-SHAPED OBTURATOR, AND SAID GEL HAVING SAID EXPLOSIVE CHARGE EMBEDDED THEREIN. 